R. W. H. ROW—REPORT ON THE SPONGES : NON-CALCAREA. odd 
Canal-system. 
Directly below the surface occur numerous small canals, which run in the 
superficial layers of the cortex in a tangential direction. Into them open the 
pores, and they themselves lead into a series of small subdermal cavities, 
which have a depth of about 0°07 mm. From these inhalant canals run down 
into the sponge, averaging 0°2 mm. wide. 
The chambers are small, very numerous, and massed together in patches. 
They measure 0:03 in diameter. 
Histology. 
There can be distinguished three regions in the cortex :— 
(i.) The dermal layer, measuring 0:1 mm. to 0:14 mm. in thickness, and 
densely packed with small stellate cells, but no apparent fibres or pigment. 
Gi.) Just below the subdermal cavities the cortex is hollowed out into a 
large number of small elongated cavities, which are filled with long rows of 
round cells. These I believe to be symbiotic algee, and if this is the case they 
would account for the dark green colour of the surface. 
Gii.) The remainder of the cortex above the chamber-layer is not to be 
distinguished from the ordinary mesoglea. 
The mesogloea is not very abundant for an Aplysina, and is filled with very 
small stellate cells. 
Locality. Agig Harbour, in 43 fathoms. 
Distribution. Red Sea. 
APLYSINA PURPUREA, Carter. 
Synonymy :— 
1880. Aplysina purpurea, Carter (7 a). 
1889. Aplysina purpurea, Dendy (12). 
1889. Psammopemma fuliginosum, Lendenfeld (20). 
? 1889. Psammaplysilla arabica, Weller (18). 
A single very fragmentary specimen has been assigned to this species on 
the strength of the structure of its skeleton ; its preservation was not suffi- 
ciently good for more to be made out of it. 
Locality. Suez. 
Distribution. Red Sea; Ceylon ; Australia. 
CACOSPRONGIA CAVERNOSA (sper). 
Synonymy :— 
1791. Spongia cavernosa, Esper (14). 
1889. Stelospongia cavernosa, Lendenfeld (with complete synonymy) (20). 
This species is represented by a single specimen. It is quite typical in 
